Multi-hypervisor consideration

My customer was considering adding a second hypervisor, because the Analysts say it is a common practice. My first thought as an IT Architect is: just because others are doing it, does not mean it is a good idea to do it. Even if it is a good idea, and it is also a best practice, does not mean it is good for you. There are many factors to consider that makes your situation and condition different to others.

Before I proceed further, we need to be clear on the scope of the discussion. This is about multi-hypervisors vs single-hypervisor. This is not hypervisor A vs B. To me, you are better off running Hyper-V or Acropolis or vSphere completely, then running >1. At least, you are not doubling complexity and need to master both. If you cannot even troubleshoot vSphere + NSX + VSAN properly, why add another platform into the mix?

To me, one needs to be grounded before making a decision. This allows us to be precise. Specific to hypervisor, we need to know which cluster should be running the 2nd hypervisor. Because of HA/DRS, a vSphere cluster is the smallest logical building block. I treat cluster as 1 unit of computing. I will make each member to have the same ESXi version and patch; hence running a totally different hypervisor in the same vSphere cluster is out of the question for me.

In order to pinpoint which cluster to run the 2nd hypervisor, you need to look at your overall SDDC architecture. This helps you ensure that the 2nd hypervisor fits well into your overall architecture. So start with your SDDC Architecture. You have that drawing right? 😉

I have created a sample for 500 server VM and 1000 VDI VM. Review that and see where you can fit the 2nd hypervisor. For those with larger deployment, the sample I provided scales to 2000 server VM and 5000 VDI VM. That’s large enough for most customers. If yours is larger, you can use that as Pod.

It’s a series of posts, and I go quite deep. So take your coffee and carefully review it.

I am happy to wait 🙂

Done reviewing? Great!

What you need to do now is to come up with your own SDDC Architecture. Likely, it won’t be as optimized and ideal as mine, as yours have to take into account brownfield reality.

You walk from where you stand. If you can't stand properly, don't walk.

Can you see where you can optimize and improve your SDDC? A lot of customers can improve their private cloud, better capability while lowering cost/complexity, by adding storage virtualization and network virtualization. If what you have is just server consolidation, then it is not even an SDDC. If you already have SDDC, but you’re far from AWS or Google level of efficiency and effectiveness, then adding a 2nd hypervisor is not going to get you closer. Focus first on getting to SDDC or Private Cloud.

Even if you have the complete architecture of SDDC, you can still lower cost by improving Operations. Review this material.

Have you designed your improved SDDC? If you have, there is a good chance that you have difficulty placing a 2nd hypervisor. The reason is a 2nd hypervisor de-optimize the environment. It actually makes the overall architecture more complex.


The hypervisor, as you quickly realized, is far from a commodity. Here is a detailed analysis on why it is not a commodity.

This additional complexity brings us the very point of the objective of a 2nd hypervisor. There are only 2 reasons why customer adds a second vendor to their environment:

  • The first one does not work
  • The first one too expensive

Optimizing SDDC Cost

In the case of VMware vSphere and SDDC, I think it is clear which one is the reason 🙂

So let’s talk about cost. With every passing year, IT has to deliver more with less. That’s the nature of the industry, hence your users expect it from you. You’re providing IT service. Since your vendors & suppliers are giving you more with less, you have to pass on this to the business.

If you look at the total IT cost, the VMware cost is a small component. If it were a big component, VMware revenue would equal to many IT giants. VMware revenue is much smaller than many IT giants, and I’m referring to just the Infrastructure revenue of these large vendors. For every dollar a CIO spends, perhaps <$0.1 goes to VMware. While you can focus on reducing this $0.1 by adding a second hypervisor, there is an alternative. You can use the same virtualization technology that you’ve applied to Server, and apply it to the other 2 pillars of Data Center. Every infrastructure consists of just 3 large pillars: Server, Storage, and Network. Use the same principles and experience, and extend virtualization to the rest of your infrastructure. Another word, evolve from Server Consolidation to SDDC.

What if Storage and Network are not something you can improve? In a lot of cases, you can still optimize your Compute. If you are running a 3-5 year old server, going to the latest Xeon will help you consolidate more. If your environment is small, you can consider single-socket. I wrote about it here. Reducing your socket counts mean less vSphere license. You can use the savings and improve your management capability with vRealize Operations Insight.

Even without this article, a lot of you realized that adding a 2nd hypervisor is not the right thing to do. I heard it directly from almost every VMware Architect/Engineers/Administrator at customers’ side. You’re trading cost from one bucket to another. This is because hypervisor is not merely a kernel that can run VMs. That small piece of software is at the core of your SDDC. Everything else on top depends on it, and leverages its API heavily. Everything else below is optimized for it. It is far from commodity. If you have peers who still think it’s a commodity, I hope this short blog article helps.

Have an enjoyable journey toward your SDDC, whichever hypervisor it maybe.

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